/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    AttributeTransformer.java
 *    Copyright (C) 2000-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.attributeSelection;

import weka.core.Instance;
import weka.core.Instances;

/**
 * Abstract attribute transformer. Transforms the dataset.
 *
 * @author Mark Hall (mhall@cs.waikato.ac.nz)
 * @version $Revision$
 */
public interface AttributeTransformer {
    // ===============
    // Public methods.
    // ===============

    /**
     * Returns just the header for the transformed data (ie. an empty set of
     * instances. This is so that AttributeSelection can determine the structure of
     * the transformed data without actually having to get all the transformed data
     * through getTransformedData().
     * 
     * @return the header of the transformed data.
     * @exception Exception if the header of the transformed data can't be
     *                      determined.
     */
    Instances transformedHeader() throws Exception;

    /**
     * Transform the supplied data set (assumed to be the same format as the
     * training data)
     * 
     * @return A set of instances representing the transformed data
     * @exception Exception if the attribute could not be evaluated
     */
    Instances transformedData(Instances data) throws Exception;

    /**
     * Transforms an instance in the format of the original data to the transformed
     * space
     * 
     * @return a transformed instance
     * @exception Exception if the instance could not be transformed
     */
    Instance convertInstance(Instance instance) throws Exception;
}
